Current-to-voltage converter and associate closed-loop control circuit

ABSTRACT

A current-to-voltage converter (10), in particular for high input voltages, comprising a primary side (14), which comprises several serially connected partial systems (16, 18, 20), including respectively at least one transistor circuit breaker (T1, T2, T3) and at least one separate associate transformer primary winding (TP1, TP2, TP3), and a secondary side (22), over which the partial systems (16, 18, 20) are coupled into a common load output (24). In order to make available a current-to-voltage converter having an uncomplicated design and partial systems with improved balanced voltage, the invention herein provides that each of the serially connected partial systems (16, 18, 20) has a branch with an input inductance (L16.1, L18.1, L20.1) and at least one transistor circuit breaker (T1, T2, T3), that the inductances (L16.1, L18.1, L20.1) are applied electrically in series to input voltage U E  at least temporarily over the corresponding transistor circuit breakers (T1, T2, T3) and produce a balanced voltage between the partial systems (16, 18, 20), and that one output each of the partial systems (16, 18, 20) is connected with respectively one transformer primary winding (TP1, TP2, TP3) acting as isolating transformer (TR1, TR2, TR3) for power supply.

FIELD OF THE INVENTION

The invention herein relates on one hand to a current-to-voltageconverter, in particular for high input voltages, with a primary side,which comprises several serially connected partial systems including,respectively, at least one transistor circuit breaker and at least oneseparate associate transformer primary winding, and with a secondaryside, over which the partial systems are coupled into a common loadoutput, and relates on the other hand relates to a current-to-voltageconverter, in particular for high input currents, with a primary side,which comprises several parallel connected partial systems including,respectively, at least one transistor circuit breaker and at least oneseparate associate transformer primary winding, and with a secondaryside, over which the partial systems are coupled into a common loadoutput, and further relates to an associate closed-loop control circuitcomprising a voltage regulator with voltage comparator and voltageamplifier and comprising a current regulator with current comparator andcurrent amplifier, as well as a correction member located between thevoltage regulator and the current regulator.

BACKGROUND OF THE INVENTION

In the case of voltage converters for high alternate input voltages ordirect voltage as known from prior art, a peak value of the rectifiedvoltage is impressed on a high-capacity capacitor located directly atthe outputs of a rectifier. Consequently, very expensive charge circuitswith pre-charging capability had to be implemented, for example, byincluding a resistor and subsequent bridging with ground contacts.

Also, so-called "double-booster" topologies have been known; thesecomprise an intermediate circuit including with an electrolyte capacitorin such a manner that the latter or the upstream mains is subjected to aload when the high input voltage is impressed due to the feedthrough,without short circuit limit. Therefore, this capacitor must beconfigured for the peak voltage at the input, whereby this peak voltageis greater than the booster's regulated output voltage.

Furthermore, in controlling high input voltages and currents, problemsoccur concerning the components used. The semiconductors such astransistors and diodes used must be adapted to the maximum input voltageor current, and the transformers used must be adapted from theviewpoints of power, as well as voltage, to the input voltage to beprocessed, whereby unacceptable winding and coil voltages occur.

In the case of known converters, which use power transistors asswitching elements, the permissible input voltage is limited by the loadcapability of the type of power transistor used. When severalsynchronously clocked transistors are connected in series and/orparallel, the problem of voltage and/or current balancing arises, oneexample of this being the connection of loss-prone RCD line branchesparallel to the transistor break distance.

DE 4,414,677 A1 has suggested a primary switched voltage converter witha primary side composed of several serially connected partial systems,each including a transistor circuit breaker arrangement, whereby each ofthese systems is associated with a separate transformer primary winding,which, in turn, are coupled into a common load output over the secondaryside of the converter. Due to the transformer winding voltage, thiscoupling effects automatic, dynamic and quasi loss-free voltagebalancing between the partial systems under load.

In the case of this form of embodiment the transformer windings areconnected "hard" parallel on the secondary side. This has thedisadvantage that the absence of balances results in dynamic circulatingcurrents--which are not current-limiting--but effect balancing.

Also this circuit layout has the disadvantage that, in the case ofconverters with alternating current input, a peak value of the rectifiedvoltage is impressed directly on a high-capacity capacitor locateddirectly at the output of a rectifier and that all of these flow-throughconverter topologies do not permit a power take-up (Power FactorCorrection=PFC) adapted to the waveform of the input voltage.

Therefore, the problem to be solved by the invention herein provides aconverter for high input voltages or input currents, said converterhaving a simple design and improving voltage or current balancing.

SUMMARY OF THE INVENTION

In accordance with the invention herein, this problem has been solved inthe case of a converter, in particular for high input voltages, in thateach of the serially connected partial systems comprises a branch withinput-side inductance and at least one transistor circuit breaker,whereby the inductances are applied, at least temporarily, over thecorresponding transistor circuit breaker electrically in series to theinput voltage and result in voltage balancing between the partialsystems, and whereby one output of each of the partial systems isconnected with the respective transformer primary winding acting asisolating transformer for power supply.

In accordance with the invention herein, this problem has been solved inthe case of a converter, in particular for high input currents, in thateach of the parallel connected partial systems comprises a branch withan input-side inductance and at least one transistor circuit breakerwhich, at least temporarily, is connected electrically parallel to inputvoltage U_(E) and thereby balances the currents between the partialsystems, and that respectively one output of the partial systems isconnected with respectively one transformer primary winding acting asisolating transformer for power supply.

As opposed to known systems, this topology results in the supply ofpower into the transformer. This means that each primary windingtransmits its current in a flow-through manner and hence impresses it onthe secondary load.

By time-synchronized activation of all transistor circuit breakers, eachpartial system works with a partial voltage or partial current, which isobtained by dividing the input voltage U_(E) or the input current I_(E)by the number N of the serially or parallel connected partial systems.In so doing, commercially available components can be used for thelayout of the transistor circuit breakers, as well as for the layout ofinductances such as reactance coils and isolating transformers, wherebythese components need not comply with high-voltage requirements. Thisreduces costs considerably. When compared with prior art, the essentialdifference is that voltage and/or current are balanced over theinput-side inductance or primary-side inductance or reactance coil ofthe corresponding partial system. Provided that all reactance coils,which are temporarily connected in series or parallel, exhibit the sameinductance and synchronous activation is ensured, on one hand aproportional voltage drop occurs on each reactance coil carrying acurrent for a certain period of time, when the connection is in series,so that also the voltage applied over the circuit elements correspondsto a N^(th) portion of the input voltage U_(E), and on the other hand aproportional current drop occurs, when the connection is parallel, sothat current flowing through the circuit elements corresponds to aN^(th) portion of the input current.

In a particularly preferred embodiment the partial systems areconfigured as SEPIC converters or regenerators, whereby at least oneconverter, preferably the reference (connected to ground) converter, isconnected with only one closed-loop control circuit, the output signalof which is supplied to a trigger circuit associated with all transistorcircuit breakers.

In another particularly preferred embodiment the closed-loop controlcircuit includes a circuit, which is connected to line voltage for thedetection of line voltage and/or line frequency, and sends correspondingsignals to the closed-loop control circuit, whereby the voltageconverter functions either as DC converter or as AC converter with PFCanalysis, depending on the input voltage. By using a mains-connecteddetector, the voltage converter can be used in a large number ofapplications. Therefore, this voltage converter system is particularlysuitable for continuous path operation using at least four UIC voltages(1000 VAC 162/3 Hz; 1500 VAC 50 Hz; 1500 VDC; 3000 VDC).

Therefore, this novel voltage converter system is capable of adapting tovarious input volt ages and/or frequencies with power take-up. Inaddition, the control parameters can be preset to the respective nominalvoltage.

For PFC analysis, a measuring element such as a shunt is associated withat least one additional reactance coil, which is coupled magneticallywith the input-side reactance coil, whereby a value g_(A) ' proportionalto the output current I_(A), preferably a DC value, can be sampled atsaid shunt. Also in this case there is the advantage that a PFC controlis possible with any input alternating voltage. Preferably, themeasuring element is located in the partial system connected with thereference potential. The value I_(A) ' may also contain an AC sharewhich occurs proportional to the input current I_(E), i.e., representinga sinusoidal half-wave function.

Another advantage of the use of SEPIC converters in the voltageconverter system introduced herein is based on the fact that theotherwise common primary storage capacitor carries out a transformationto the low-voltage side or secondary side at the rectifier output or inthe intermediate circuit and is charged there by short-circuit currentcontrol. As a result, the otherwise available storage capacitor iswithdrawn from the primary direct access of the input voltage. For thisreason, electrolytes can be omitted at the input (high-voltage circuit),and electrolytes can be transformed into the secondary circuit (low-voltage circuit).

Due to the input-side series or parallel connection of the convertersactivating the isolating transformers, the converters themselves may bedesigned for 1/N times the total output, whereby N represents the numberof partial systems that are connected in series or parallel.

Therefore, also the voltage or current per turn of the individualcurrent isolating transformers can be correspondingly lower.

In a preferred form of embodiment the output voltage of thecurrent-to-voltage converter system can be adjusted to various outputvoltages. This is achieved specifically by activating the transistorcircuit breakers located in the partial systems. Also in this case it ispossible to associate one primary winding on a core with severalsecondary windings having different numbers of turns per unit length.

In this case the transistor circuit breakers located in the partialsystems can be activated over a transmitter provided on one core,thereby ensuring the time-synchronous activation of the transistorcircuit breakers that are connected in series or parallel. Furthermore,the primary winding of the isolating transformer is coupled over a diodewith a corresponding output of the SEPIC converter. This ensures thatreverse currents of the isolating transformer do not affect the SEPICconverter negatively and that the free demagnetization of the currentisolating transformer is possible.

Furthermnore, the primary windings are wound on the same core and act ona secondary winding.

Furthermore, in accordance with the invention herein, a closed-loopcontrol circuit for a current-to-voltage converter has been suggested,which comprises a voltage regulator with voltage comparator and avoltage amplifier, as well as a current regulator with currentcomparator and current amplifier, as well as a correction member locatedbetween the voltage regulator and the current regulator.

The closed-loop control circuit comprises a circuit for the detection ofline voltage and/or line frequency, whereby this circuit is connectedwith a sampling circuit, which, in turn, is connected with one input tooutput voltage and with one output to the first input of a voltagecomparator, and whereby the voltage regulator is connected on its outputside with a preferably multiplying D/A converter, which, in turn, isconnected with its second input with an output of the circuit and withits output side with an input of the current comparator of the currentregulator.

By detecting the line voltage and the line frequency, the closed-loopcontrol circuit can be set to different input voltages and/orfrequencies. The said circuit makes corresponding control parametersavailable. Consequently, a PFC analysis may be performed at any inputalternating voltage (amplitude, range and frequency). As an alternative,the rectified input voltage (downstream of the rectifier) may be sampledor detected.

In order to ensure an accurate detection of the line voltage and theline frequency, whereby the line voltage can also be a DC voltage, thecircuit is configured as an integrated circuit, preferable asmicroprocessor or micro-controller. Depending on the detected mainsparameters, a synthetic function with constant amplitude B (with DCinput) or a pulsed sine function B_(max) | sin (ωt)| (with AC input) maybe made available in phase and synchronous to the mains input, thelatter representing the actually synchronized line frequency. Then theerror-amplified voltage difference k_(U) ×ΔU_(A) can be multiplied withthe digital sine function available at the micro-controller output. Toachieve this, the D/A converter, to which the digital sine of thecircuit is supplied, follows downstream the voltage amplifier. At theoutput of the D/A converter a sine-modulated, error-amplified voltagecan be sampled, which is available as nominal value to the downstreamcurrent-regulating circuit.

The advantage of this novel closed-loop control circuit layout is that acorrection due to input voltage changes is not necessary. In particular,the correction member does not require correction as a function of theinput voltage U_(E). In addition, the actual current I_(AIst) suppliedto the closed-loop control circuit is independent of the fluctuations ofinput voltage U_(E).

Furthermore, pre-programmed sine functions are stored in the circuit,whereby digital values can be multiplied and utilized by the D/Aconverter downstream the voltage converter.

Furthermore, the synthetic sine generated in the circuit is utilized asreference for continuous detection of undervoltages and overvoltages.

And, furthermore, the closed-loop control circuit comprises a comparatorcircuit integrated in the switching circuit, with which said comparatorcircuit the synthetic sine applied to the output of the switchingcircuit is synchronized relative to the power mains.

If the line voltage does not have zero crossings, i.e., an input voltageis concerned, the switching circuit generates a constant value B so thatthe closed-loop control circuit functions as DC regulating circuit and aPFC analysis does not occur in this case.

As a result of the above measures, the field of use of the voltageconverter system may be expanded considerably, so that specifically incontinuous path applications at least four UIC voltages (1000 VAC 162/3Hz, 1500 VAC 50 Hz, 1500 VDC, 3000 VDC) or 48/60/110/220 VDC and 110/234VAC 60/50 Hz power mains can be controlled as input voltage rangeconverters. Inasmuch as the converter or regenerator permits very wideinput voltage ranges, the problem of determining DC input voltages or ACinput voltages with varying frequencies has been solved by the describedmethod, so that all four voltage ranges plus tolerances (+/-30%) andlong-term transients can be processed in one input voltage range. Also,DC input voltages having a particularly high proportion of alternatingvoltages can be controlled preferably without peak currents. Inaddition, it is possible to preset a few control parameters to thenominal voltage (T_(On) time).

The method of the invention herein is distinguished in that the primarypartial systems are operated with non-pulsating current and such partialsystems are cascaded for the first time. These partial systems representso-called "reactance-analyzed" topologies, which do not use pulsatingcurrent to the input. In addition, in accordance with the inventionherein, the PFC analysis of the cascaded partial systems occurs in onestage on only one partial system, whereby, however, the entire system issubjected to PFC analysis.

Based on the method herein, control variables or monitoring functions donot require feedback by complex, potential-isolating measures. This isachieved in that the output current can be measured as "average" valueon the primary side. In addition, the output voltage can be measured onthe primary side on the primary-side transformer winding during theT_(Off) time. Advantageously, the input voltage U_(E) can be measured onthe secondary side on a secondary winding during the T_(On) time.

A correction of the closed-loop control circuit over the input voltageU_(E), as has been known from prior art closed-loop control circuits, isnot necessary in the case of the inventive closed-loop control circuitbecause the line voltage/input voltage is pre-given by the switchingcircuit and the value proportional to the output current is not afunction of input voltage fluctuations.

Furthermore, a current-to-voltage converter in accordance with claim 1exhibits independent inventive character. On its primary side it hassubstantially the layout of a partial systems of the already describedcascaded current-to-voltage converter, however, on its output side ithas multiple outputs with separate secondary windings which areenergized through the primary winding over a joint core. Inasmuch as theisolating transformer is supplied with power, the output voltages of themultiple outputs are determined solely based on the winding ratio of thenumbers of turns per unit length of the primary winding to the secondarywinding. The individual currents are divided corresponding to theinternal impedance of the load acting on the individual outputs.Therefore, the output voltages are constant even with changing loadcurrents.

Also in this case the current-to-voltage converter is operated withnon-pulsating current. The output values, again, can be measured on theprimary side and fed to the above-described closed-loop control circuit.

As an alternative, an additional winding or a secondary winding and/orthe primary winding itself may be configured as a measuring winding inorder to produce signals for the closed-loop control circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional details, advantages and features of the inventionherein--individually and/or in combination--are disclosed by the claims,as well as by the subsequent description of diagrams that refer topreferred examples of embodiment. They show:

FIG. 1 is a circuit diagram showing a cascaded current-to-voltageconverter with three primary-side serially connected partial systems,whereby these partial systems are configured as SEPIC converters,

FIG. 2 is a circuit diagram showing a current-to-voltage converter withthree primary-side parallel connected partial systems,

FIG. 3 is a circuit diagram showing a closed-loop control circuit for atleast one partial system of the voltage converter system in accordancewith FIG. 1 or FIG. 2, and

FIG. 4 is a circuit diagram showing a current-to-voltage converter withsecondary-side multiple outputs.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a current-to-voltage converter 10, which is connected to aline voltage U_(Netz) over a rectifier 12 having diodes D1 through D4.In this form of embodiment line voltage U_(Netz) typically ranges within1000 and 1500 VAC and can have a frequency of 162/3 Hz to 400 Hz. Inputvoltages within the range of 1500 VDC and 3000 VDC are also possible. Inthe example of embodiment illustrated here a sinusoidal pulsating,half-wave-shaped input alternating voltage UE is applied to the outputof rectifier 12, said voltage U_(E) being converted into a constantoutput voltage U_(A) by voltage converter 10.

Current-to-voltage converter 10 has a primary side 14 including severalserially connected partial systems 16, 18, 20, each including at leastone transistor circuit breaker T1, T2, T3. In the example of embodimentillustrated here, partial systems 16, 18, 20 are configured as SEPICconverters or regenerators, the outputs of which are respectivelyconnected with a primary winding TP1, TP2, TP3 of an isolatingtransformer TR1, TR2, TR3. Each of isolating transformers TR1, TR2, TR3has secondary coils TS1, TS2, TS3, which are coupled into a joint loadoutput 24 over secondary side 22 of voltage converter 10.

The design of a SEPIC converter with reference to partial system 20 isdescribed hereinafter as example. Partial system 20 comprises a SEPICconverter 26, a primary side input 28 connected with an inductance suchas an input reactance coil L20.1, which is connected over a capacitor 30and a diode 32 with a first terminal 34 of transformer primary windingTP3. Another terminal 36 is connected with a primary-side output 38 ofSEPIC converter 26. Between input-side reactance coil L20.1 andcapacitor 30 is a connection point 40, which is connected with a firstterminal 44 of transistor circuit breaker T3 over a series network 42.Another terminal 46 of transistor circuit breaker T3 is connected withoutput 38. A control input 48 of transistor circuit breaker T3 isconnected with output 38 over a secondary winding of a transmitter 50.Between capacitor 30 and diode 32 is a connection point 52, which isconnected with output 38 over a second reactance coil L20.2 and aresistor 56 such as a shunt. Parallel to the primary-side transformerwinding TP3 is a relief network consisting of a capacitor 58 and aresistor 60 connected in series.

On the secondary side, secondary winding TS3 of transformer TR3 isconnected with a peak value rectifying circuit 62 consisting of diodeD5, the output of which is connected to a capacitor 64. Secondarywinding TS2 is also connected on the load side with a rectifying circuit66, the output of which is connected to a capacitor 68. The same appliesto secondary winding TS1, which is connected on the load side with arectifying circuit 70, the output of which is connected to a capacitor72. Secondary side 22 consists substantially of three secondary systems74, 76, 78, each consisting of respectively the secondary transformerwinding, the associate rectifier and the output capacitor. Secondarysystems 74, 76, 78 are electrically connected parallel and form anoutput 80, at which the controlled output voltage U_(A) can be sampledover a filter network 82. Capacitors 64, 68, 72 may also be configuredas a single joint capacitor with high capacity.

Preferably, the windings of the isolating transformers are located on aseparate transformer core 84, 84', 84". However, a possible alternativeis to locate the windings on a joint core if the ratio of voltages tocurrents is suitable.

Due to the primary-side serial connection of the regenerators or SEPICconverters, which are electrically isolated, the voltage drop on onetransistor circuit breaker T1, T2, T3 is reduced to one third of inputvoltage U_(E). This is the reason why transistors with commercialelectric strength can be used. Due to time-synchronized activation ofprimary-side partial systems 16, 18, 20 over transmitters 50, 50', 50",each step is connected with one third of input voltage U_(E). To achievetime-synchronized activation, the activation windings of transmitters50, 50', 50" are located on one common magnetic core. However, apossible alternative is the configuration of the activation windings asseparate transformers, specifically in cases of very high inputvoltages.

When transistor circuit breakers T1, T2, T3 are activated, a currentflows from positive pole 86 of rectifier 12 over input reactance coilL16.1 of partial system 16, a series network 42" and transistor circuitbreaker T1, as well as over input reactance coil L18.1, snubber element42' and transistor circuit breaker T2, as well as over input reactancecoil L20.1, series net element 42 and transistor circuit breaker T3 tonegative pole 88 of the rectifier. Inasmuch as the current through inputreactance coils L20.1, L18.1 and L16.1 is identical--the same reactancecoil inductances and synchronous activation of transformer switchelements T1, T2, T3 provided--the same voltage drop will occur on eachreactance coil L16.1, L18.1, L20.1, as a result of which an equalvoltage drop is set on transistor circuit breakers T1, T2, T3.

If the input is DC, capacitors 90, 90', 90" are parallel to the inputsof the respective partial systems 16, 18, 20, whereby respectively only1/3 of the input voltage U_(E) drops at each capacitor. In the presentcase, the usually very large storage capacitor is withdrawn from theprimary direct access of the input voltage and transformed to thelow-voltage or the secondary side and charged there by short-circuitcurrent.

FIG. 2 shows a current-to-voltage converter 92 which is connected over arectifier 94 with diodes D6 through D9 to line voltage U_(Netz). In thisexample of embodiment the line voltage U_(Netz) typically is within therange of 110-234 VAC or 28-48 VAC and can have a frequency of 162/3Hz-400 Hz. Line voltages within the range of 4-72 or 14.4-154 VDC arealso possible. Current-to-voltage converter 92 is designed specificallyfor high input currents I_(E) or output currents I_(A).

Current-to-voltage converter 92 has a primary side 96 including severalparallel connected partial systems 98, 100, 102, each including at leastone transistor circuit breaker T4, T6, T7. In the example of embodimentshown here, partial systems 98, 100, 102 are configured as SEPICconverters or regenerators, the outputs of which are connected withrespectively one primary winding TP4, TP5, TP6 of an isolatingtransformer TR4, TR5, TR6. Each of isolating transformers TR4, TR5, TR6has secondary coils TS4, TS5, TS6, which are coupled over a secondaryside 104 of current-to-voltage 92 into ajoint load output 106.

The layout of partial systems 98, 100, 102 corresponds substantially tothat of partial systems 16, 18, 20, which have been described in detailwith reference to FIG. 1. As a result of the primary-side parallelconnection of the electrically isolated regenerators or SEPIC converters98, 100, 102 the current flowing through a transistor circuit breakerT4, T5, T6 is reduced to one third of input current I_(E). This is thereason why transistors with commercial electric strength can be used.Due to time-synchronized activation of primary-side partial systems 98,100, 102 by activation transmitters 108, 110, 112 one third of inputcurrent I_(E) flows through each step. To achieve time-synchronizedactivation, activation transmitters 108, 110, 112 of the parallelcircuit described here are located on one common core. Activationtransmitters 108, 110, 112 can also be configured as electronicsemiconductor power drivers (not illustrated). Partial systems 98, 100,102 have input-side inductances L98.1, L100.1, L102.1, which, over thetransistor circuit breakers, are connected parallel to input voltageU_(E) at least temporarily and therefore have a current-balancing effecton the entire system.

FIG. 3 shows the closed-loop control circuit which is used to explainhow the current-to-voltage converter is controlled.

FIG. 3 shows the closed-loop control circuit for activation of a partialsystem 16, 18, 20 or 98, 100, 102 of current-to-voltage regulator 10 or92 in accordance with FIG. 1 or 2, respectively. Closed-loop controlcircuit 200 has an input-side voltage comparator 202, the first input204 of which is connected with reference voltage U_(ARef) and the secondinput 206 of which is connected over a sampling circuit 208 such as asample-and-hold circuit or continuous measurement, with output voltageU_(A) for sampling an actual voltage U_(AIst). Output voltage UA ismeasured over a not-illustrated measuring element on output 24 of thecurrent-to-voltage converter or over load voltage U_(A) ' on primarytransformer winding TP1 through TP6 during the T_(OFF) phase.

An output 210 of comparator 202 is connected with an input 212 of anamplifier 214 in order to amplify an error voltage ΔU_(A) resulting fromactual voltage U_(AIst) and reference voltage U_(ARef). To an output 216of amplifier 214 an error-amplified voltage K_(U) ×ΔU_(A) is connected,said voltage being applied to an input 218 of a multiplying D/Aconverter 220. Another input 222 of D/A converter 220 is connected withan output 224 of a switching circuit, preferably micro-controller 226.Micro-controller 226, in turn, is connected over lead 228 with a powerline or line voltage U_(Netz). Furthermore, micro-controller 226 isconnected over output 230 and a trigger line 232 with an input 234 ofsampling circuit 208.

An output 236 of D/A converter 220, to which a nominal current I_(ASoll)is applied, is connected with an input 238 of a comparator 240. Anotherinput 242 of comparator 240 is connected over lead 138 with shunt 56 inthe branch of reactance coil 220.1 for sampling a value I_(A) ' which isproportional to output current I_(A). An output 244 of the comparator isconnected with an input 246 of a current amplifier 248. An output 250 ofthe amplifier is connected to an amplified error current K_(I) ×ΔI_(A),which is fed to an activation unit 252 and forms a control variable. Theactivation unit also comprises an input 254 for the line or inputvoltage for T_(ON) control, as well as an output 256 for activation oftransistor circuit breaker T1 or T6 over activation transmitter 50, 50',50" or 108 through 112. The value K_(I) ×ΔI_(A) is used for control ofthe T_(Off) time of transistor circuit breakers T1-T6. Even without U/Icontroller, a quasi-constant output voltage with sinusoidal currenttake-up with alternating power supply and varying input range or outputload is achieved by means of T_(ON) control and preset T_(OFF) voltageas DC value.

Over input line 228, micro-controller 226 detects input line voltageU_(Netz), as well as line frequency f_(Netz). If line voltage is directvoltage, frequency f_(Netz) =0 is detected. Any frequency may bedetected, preferably f=162/3, 50 or 60 Hz. Based on the detected linefrequency, a synthetic, ideally pulsating (rectified) sine function isstored and generated in micro-controller 120, whereby this sine functionis synchronized with the line frequency and has a constant amplitudeB_(max).

After detection and storage of the time base, processing begins with atrigger/zero crossing, and synchronization occurs during additional zerocrossings. Synchronization pulses between mathematical zero crossingsare gated because of possible interferences.

Over output 224, the generated sine curve is fed to input 226 of D/Aconverter 220. When a synchronization pulse, which is available for eachhalf-period zero crossing, is present, sampling circuit 208 istriggered. Now the error-amplified voltage error voltage K_(U) ×ΔU_(A)is multiplied with the synthetic sine curve B_(max) ×| sin (ωt)|, whichis in phase with line voltage, in D/A converter 220. Therefore, asine-analyzed voltage-error-amplified value is at the output, wherebythis amplified value is available as nominal current I_(ASoll) for theactivation of transistor circuit breakers T1-T6.

As opposed to known closed-loop circuits, an additional correctionmember is not required because a value is available due to themeasurement of the output current in the primary-side reactance coilbranch, said value being independent of long-term fluctuations of inputvoltage U_(E), but follows the waveform of the nominal frequency (PFC).

Inasmuch as the sine function is generated by the micro-controller, itmay also be used as reference for undervoltage and overvoltagedetection. The sine function generated by the micro-controller can besynchronized to mains by means of a comparator circuit. Ifmicro-controller 226 detects that the input voltage is a direct voltage,a constant voltage B is output at output 224 so that PFC analysis is notnecessary.

Concerning the output voltage actual value U_(AIst), it should bementioned that it is sampled by the trigger of the sine zero crossing,stored in sample-and-hold circuit 208 and compared with reference valueU_(ARef).

The described system comprising current-to-voltage converter 10, 92 andinventive closed-loop control circuit 200 is used in particular incontinuous path operation using at least four UIC voltages as, forexample, 1000 VAC 162/3 Hz, 1500 VAC 50 Hz; 1500 VDC and 3000 VDC.Inasmuch as the voltage converter or regulator permits a wide inputvoltage range, the problem of determining input alternating voltage orinput direct voltage or frequency of input alternating voltage has beensolved by the described method. All four ranges and tolerances (+/-30%)and long-term transients can be processed in one input voltage range.

FIG. 4 shows a current-to-voltage converter 400 with independentinventive characteristics. Current-to-voltage converter 400 has aprimary side 402, which is connected over a rectifier 404 to linevoltage U_(Netz), and a secondary side 406, which has several, i.e.,multiple, preferably three outputs 408, 410, 412 with output voltagesU_(A1), UA₂, U_(A3).

Connected parallel to output terminals 414, 416 of rectifier 404 is acapacitor 418, to which is applied an input voltage U_(E) forcurrent-to-voltage converter 400. Terminal 414 is connected with aprimary inductance such as reactance coil L420.1, which is connectedover a capacitor 422 and a diode 424 with a first terminal 426 of aprimary-side winding TP7 of an isolating transformer TR. One terminal428 of primary-side winding TP7 is connected with input terminal 416 ofrectifier 404. Between reactance coil L420.1 and capacitor 422 is aconnecting point 430, which is connected over a snubber network 432 anda transistor circuit breaker T7 with terminal 416. A control terminal434 of transistor circuit breaker T7 is connected over a secondarywinding 436 of an activation transmitter 438 with terminal 416.

A connecting point 440 located between capacitor 422 and diode 424 isconnected over a second inductance such as reactance coil L420.2 and aserially connected measuring element such as shunt 444 with clamp 416 aswell. The secondary-side multiple outputs 408, 410, 412 each have asecondary winding TS7.1, TS7.2, TS7.3 that are located, together withprimary winding TP7, on a joint core 446. Secondary windings TS7.1,TS7.2, TS7.3 are connected over a rectifier diode 448, 450, 452 with anoutput capacitor 454, 456, 458, to which output voltages U_(A1), U_(A2)and U_(A3) are applied.

The closed-loop control circuit described in conjunction with FIG. 3 canbe used for control of current-to-voltage converter 400. Alsocurrent-to-voltage converter 400 is characterized in that feedback ofcontrol variables or monitoring functions of secondary-side values isnot necessary. This is possible in particular in that the output voltagecan be measured on the primary side during the T_(Off) time at terminal426 of primary winding TP7 and the output current (average value) on theprimary side at measuring element 440. During the T_(On) time the inputvoltage can be measured on the secondary side.

I claim:
 1. A current-to-voltage converter (10) having a primary side(14), which comprises a plurality of serially connected partial systems(16, 18, 20), and with a secondary side (22), over which the partialsystems (16, 18, 20) are coupled into a common load output (24),whereineach of the serially connected partial systems (16, 18, 20)comprises respectively at least one transistor circuit breaker (T1, T2,T3) and at least one separate associate transformer primary winding(TP1, TP2, TP3), and has a branch with an input inductance (L16.1,L18.1, L20.1) and at least one transistor circuit breaker (T1, T2, T3),such that the inductances (L16.1, L18.1, L20.1) are applied electricallyin series to an input voltage (U_(E)) at least temporarily over thecorresponding transistor circuit breakers (T1, T2, T3) and to produce abalanced voltage between the partial systems (16, 18, 20), and that oneoutput each of the partial systems (16, 18, 20) is connected withrespectively one transformer primary winding (TP1, T2, TP3) acting asisolating transformer (TR1, TR2, TR3) for power supply.
 2. Acurrent-to-voltage converter (92) having a primary side (96), whichcomprises a plurality of parallel connected partial systems (98, 100,102), and with a secondary side (104), over which the partial Systems(98, 100, 102) are coupled into a common load output (106), whereineachof the parallel connected partial systems (98, 100, 102) comprisesrespectively at least one transistor circuit breaker (T4, T5, T6) and atleast one associate transformer primary winding (TP4, TPS, TP6), and hasa branch with an input inductance (L98.1, L100.1, L102.1) and at leastone transistor circuit breaker (T4, T5, T6), such that the inductances(L98.1, L100.1, L102.1) are applied electrically parallel to an inputvoltage (U_(E)) at least temporarily over the corresponding transistorcircuit breakers (T4, T5, T6) and to produce a balanced current betweenthe partial systems, and that one output each of the partial systems isconnected with respectively one transformer primary winding (TP4, TP5,TP6) acting as isolating transformer (TR4, TR5, TR6) for power supply.3. Current-to-voltage converter in accordance with claim 1, whereintheisolating transformers (TR1-TR3 and TR4-TR6) are configured as currenttransformers and that each has a separate magnetic core. 4.Current-to-voltage converter in accordance with claim 1, whereinthepartial systems (16, 18, 20, 98, 100, 102) are configured as a SEPICconverter (26, 26', 26") or as a regenerator.
 5. Current-to-voltageconverter in accordance with claim 1, whereinonly one partial system,preferably the partial system connected to a reference potential(ground), is connected with a closed-loop control circuit (200). 6.Current-to-voltage converter in accordance with claim 1, whereintheclosed-loop control circuit (200) includes a circuit (226) connected toline voltage in order to detect line voltage and/or line frequency andthat the circuit (226) transfers corresponding signals to theclosed-loop control circuit (200) so that, depending on the inputvoltage, the current-to-voltage converter (10, 92) is adapted as DCconverter or as AC converter with PFC analysis.
 7. Current-to-voltageconverter in accordance with claim 1, whereinthe converter can beconnected, without switchover, to international UIC voltages, preferably1000 VAC 162/3 Hz, 1500 VAC 50 Hz and 1500 VDC to 3000 VDC. 8.Current-to-voltage converter in accordance with claim 1, whereinat leastone measuring element such as a shunt is associated with an additionalinductance such as the reactance coil (L16.2, L18.2, L20.2; L98.2,L100.2, L102.2), which is magnetically coupled with the correspondinginput-side inductance such as reactor (L16.1, L18.1, L20.1; L98.1,L100.1), whereby a value I_(A) ' proportional to output current I_(A)can be sampled at said measuring element.
 9. Current-to-voltageconverter in accordance with claim 1, whereinthe transformers (TR1, TR2,TR3) produce an output corresponding to 1/N times the total output,whereby N represents the number of serially or parallel connectedpartial systems.
 10. Current-to-voltage converter in accordance withclaim 1, whereinthe current-to-voltage converter has multiple outputvoltages, whereby the output voltages of the cascaded current-to-voltageconverters (10, 92) is pre-controlled proportional to 1/U_(E) by T_(On)time and set and adjusted through T_(Off).
 11. Current-to-voltageconverter in accordance with claim 1, whereinthe transistor circuitbreakers (T1-T6) included in the partial systems (16, 18, 20) can beactivated over a trigger element such as an activation transmitter (50,50', 50") by means of a T_(On) time per unit area. 12.Current-to-voltage converter in accordance with claim 1, whereintheprimary winding (TP1, TP2, TP3) of the isolating transformer (TR1, TR2,TR3) is coupled over a diode (32, 32', 32") into the correspondingoutput of the SEPIC converter (26, 26', 26") for power supply. 13.Current-to-voltage converter in accordance with claim 1, whereinat leastone of the primary windings (TP1, TP2, TP3) is associated with severalsecondary windings (TS1.1, TS1.2, TS1.3), which preferably havedifferent numbers of turns per unit length in order to create multipleoutputs.
 14. Method for controlling the current-to-voltage converter ofclaim 1, whereby an output voltage (U_(A)) and an output current (I_(A))are detected and compared with setpoints in order to generate acontrolled variable, whereina line voltage and/or a line frequency aredetected, such that a trigger signal is generated as a function of theline frequency in order to sample the output voltage, that a syntheticsine or a constant digital value is generated as a function of the linefrequency, that the generated sine or constant digital value isconverted into an analog value and multiplied with an amplified errorvoltage K_(U) ×ΔU_(A) in order to generate a setpoint for the outputcurrent I_(A).
 15. Method in accordance with claim 14, wherein aplurality of primary partial systems (16, 18, 20; 98, 100, 102) areoperated with non-pulsating current.
 16. Method in accordance with claim14, wherein a PFC analysis of a plurality of cascaded partial systems(16, 18, 20, 98, 100, 102) is performed in one stage on one partialsystem (20, 102).
 17. Method in accordance with claim 14, wherein theinput voltage (U_(E)) is measured on the output side via T_(On) time.18. Method in accordance with claim 14, wherein a value (U_(A) ')proportional to the output voltage (U_(A)) and a value (I_(A) ')proportional to the output current (I_(A)) are measured on the primaryside.
 19. Method in accordance with claim 14, wherein a correction of aclosed-loop control circuit over the input voltage (U_(E)) isunnecessary.